| Recent years, with the rapid development of our national highway construction, total course of freeway has already taken the second place in the world. The accelerated highway construction and improved highway network has greatly prompted the national economy. However, as highway course is increasing, various premature problems have come to the fore. Except for the defect of technical standards and regulations and over-loaded vehicles, the obvious lacking of quality management and that the inspection of the asphalt concrete pavement failed to meet the requirements of compliance examination of its design are also be considered as major causes. Pavement cores are the best inspecting method for completed pavement. Therefore, the Semi-Circular Bending (SCB) test, which is chosen as its test specimens, is of great significance. Based on the SCB test, this paper has discussed dynamic modulus, fracture toughness and fatigue fracture performance of asphalt concrete, giving an analysis on the evolution rules of asphalt concrete fatigue process from the view of energy consumption.First of all, the paper analyzes a load response of semicircular specimens with two-dimensional finite element method, giving a stress coefficient fitted equation and a displacement coefficient fitted equation of two specimens, the diameters of which are 150mm and 100mm, in different distance of fulcrums. According to the specimens sizes in this research, stress and displacement response of the specimens under load is analyzed with three-dimensional finite element method to get the results of stress distribution and displacement coefficient in the tensile zone at the bottom of the specimens, which lay the theoretical analysis foundation for this research to carry mechanical tests out. Meanwhile, the causes for different researchers giving different stress coefficients are also explained here. There is also a contrastive analysis between semi-circular flexural-tensile strength and indirect tensile strength for asphalt mixture at different temperature. As a result, the former obviously exceeds the latter, while the latter is more sensitive to the temperature, i.e., the transformational relation between the two is relevant to the temperature.Based on three-dimensional finite element analysis results in the semi-circular bending test, we have developed a measuring method of the semi-circular bending dynamic modulus, with which we have measured the bending dynamic modulus and the phase angle of different asphalt mixtures at different temperatures and frequencies. Besides, we also have got the asphalt mixture dynamic modulus master curve on the basis of time-temperature equivalence principle. According to the test result of the same batch of specimens, we made two contrastive analyses: semi-circular bending dynamic modulus master curve and uniaxial compression dynamic modulus master curve; indirect tensile dynamic modulus master curve and shearing dynamic modulus master curve. We found that the uniaxial one is visibly greater than the semi-circular one and the indirect one, while the semi-circular one is similar to the indirect one, and the shearing one is clearly less than the previous three ones. Based on the mathematical model from Sigmoidal, we set the transformational relation among semi-circular bending dynamic modulus and uniaxial compression dynamic modulus and shearing dynamic modulus.Based on J Integration Theory, using semi-circular specimens of different crack lengths, this paper gives a contrastive analysis on the anti-cracking ability of three different graded asphalt mixtures at the stress absorbed layer, evaluating the J integration fracture resistance, JIC, of 4 different graded asphalt mixtures at different temperatures. The test result shows that the asphalt mixture at the stress absorbed layer with skeleton structure design has better anti-cracking ability, and that JIC decreases as the temperature falls, i.e., the anti-cracking ability decreases as the temperature falls. In this paper, we get the stress intensity factor fitted equation for the crack tip of the semi-circular specimen with the method of finite element, and make a contrastive analysis on JIC and KIC. As a result, JIC makes it suitable for evaluating the anti-cracking ability of asphalt mixtures. From the test results, this paper gives a half-experience and half-theory based separate specimen JIC predictor formula of the semi-circular bending test.Moreover, in terms of fracture mechanics theory, this paper gives a design of Fatigue Cracking test. Through graphics techniques, the relation between load times (N) and crack growth length (a) was gained. In view of nonhomogeneity of the asphalt mixture and noncontimuity of its crack growth, and taking overall growth trend of the fatigue cracking into account, we put forward the method of N-a fitted curve with 2 Exponential Growth Function, and got that, in the log-log coordinate, there is an obvious situation of crack growth three-stage in the crack growth rate and the stress intensity factor amplitudeΔK, with the data of minor discreteness character. The effect of load frequency and stress ratio on asphalt mixture crack growth rate is also analyzed in this paper. According to Paris Formula, we got the crack growth rates of different common asphalt mixtures at three layers at 15℃and 0℃, and the coefficients of the fitted Paris Formula can provide reference for the pavement anti-cracking design. And also based on CT scanning technique, we got the crack tip status of the asphalt mixture, and analyzed the cause for the fatigue life differentiation of the asphalt mixture specimens.Through Fatigue Energy Consumption Principle, this paper gives an analysis on the fatigue evolution rule of asphalt mixtures. Meanwhile, according to fatigue process displacement diagram, the paper defines fatigue fail point, analyzing total fatigue cracking energy and single fatigue cracking energy during the process of asphalt mixture crack growth, setting up Fatigue Energy Consumption Predictive Equation based on fracture toughness and dynamic modulus. Integrated with the energy consumed in the four-points bending fatigue test, it also analyzes the effect factors to fatigue life based on energy consumption, and applicated the concept of energy consumption to macro-fatigue-crack-growth process.
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